The specific operation method for leveling the middle line in the cdr line menu is as follows:

1. First, double-click to open the cdr software, and then click to open the file.

2. Then click [Select Tool] on the toolbar to select the graph.

3. Click the small triangle [Shape Tool] in the lower right corner of the toolbar to pop up the option, and select Smooth.

4. Finally, click the mouse to drag along the edge of the curve, and click OK to return to the page. You can see that the chart has become smooth.